If you’ve walked in New England woods recently, chances are great that you’ve noticed light tan moths with a one-inch wing span flitting about — an odd sight for this late in the year. These are male Bruce Spanworm Moths (Operophtera bruceata), also called Winter Moths, as the adults are active from October to December. They belong to the Geometer family of moths, the second largest family of moths in North America, which includes many agricultural and forest pests. The males are seeking wingless, and therefore flightless, females to mate with. Eggs are laid in the fall, hatch in the spring, the larvae pupate in the summer, and emerge as adult moths in the fall. Bruce Spanworm larvae periodically defoliate hardwood trees, preferring the buds and leaves of sugar maple, American beech and trembling aspen trees.
You could hardly be blamed for not recognizing that this bright yellow-green, half-inch-long, oval creature is the larval stage of a moth! Possessing suction cups rather than prolegs, the Yellow-shouldered Slug (Lithacodes fasciola) glides, rather than crawls, over the leaf it is consuming. Perhaps this is why these caterpillars show a preference for smooth-leaved trees and shrubs such as basswood, beech, cherry, maple and oak (although this particular individual was found on a witch-hazel leaf). The Yellow-shouldered Slug pupates inside a cocoon all winter, and in the spring a small, brown moth emerges.
The Spined Soldier Bug is a predatory stink bug which preys on a variety of other insects (over 90 species), especially the larvae of butterflies, moths and beetles. It is one insect that farmers actually welcome, as it preys heavily on the larvae of the European corn borer, Mexican bean beetle, cabbage looper, Colorado potato beetle, flea beetles and many other crop pests. The adult Spined Soldier Bug has a prominent spine on each “shoulder.” It also has piercing-sucking mouthparts which it uses to impale prey and suck out their internal juices. The photograph shows a Spined Soldier Bug dining on the innards of a monarch caterpillar.
The Viceroy Butterfly closely resembles the Monarch Butterfly, but is smaller, and has a black line that runs across the veins of its back wings, which the Monarch lacks. While Viceroys don’t contain the poisonous cardiac glycosides that Monarchs do, they do contain salicylic acid due to fact that the larvae feed on willows. This acid not only causes the Viceroy to taste bad, but makes whatever eats it sick. So not only do these two butterflies look alike, but they discourage predators in the same way. This is not a coincidence. The fact that they are both toxic if eaten and are preyed upon by some of the same predators has led to their similar appearance. This phenomenon is referred to as Müllerian mimicry, and essentially it means if two insects resemble each other, they both benefit from each other’s defense mechanism — should a predator eat one insect with a certain coloration and find it inedible, it will learn to avoid catching any insects with similar coloration.
Of all the insects I’ve found in milkweed patches over the years, the Hummingbird Clearwing is one of my favorites. It is a species of sphinx moth, named for its habit of hovering at flowers while it gathers nectar with its proboscis in a manner similar to that of hummingbirds. In fact, they are often mistaken for hummingbirds. The transparent wings, light brown thorax and dark chestnut abdomen are the field marks to look for. A diurnal moth, the Hummingbird Clearwing can often be found during the day in milkweed patches.
If you’ve been traveling on sunny dirt roads lately, chances are that you have seen White Admiral butterflies all over them. They are in the road to obtain salts and minerals that have leached from the soil into standing puddles and moist dirt. Because butterflies do not have chewing mouthparts as adults, they must drink their meals. While nectar is their main source of nutrition, males often supplement their diet with these minerals. The act of acquiring nutrients in this manner is referred to as “puddling.” If there’s no water around, a butterfly may regurgitate into the soil and then drink in the hope of retrieving minerals. In addition to finding butterflies on dirt roads, look for them puddling on animal scat.
With the warm temperatures this week, mourning cloak butterflies have been seen gliding through the leafless woods. Like eastern commas, question marks and red admirals, mourning cloaks overwinter as adults. They resemble dead leaves so much that from a distance the entire insect seems to disappear. Up close you can see the velvety texture of the wing scales, said to resemble the clothing mourners used to wear; hence, their common name. Mourning cloaks live up to ten months — an impressive life span for a butterfly. As they age, the yellow border of their wings fades to an off-white.
The striped caterpillar that is crawling along the surface of fresh snow is the larval stage of a noctuid or owlet moth (species unknown). Noctuids are dull-colored, medium-sized, nocturnal moths that are attracted to lights in the summer. They usually possess a well-developed proboscis (mouthpart) for sucking nectar. You may be familiar with the common garden pests, cutworms, which are also noctuid larvae. How this larva survives freezing temperatures I do not know, but I have seen several dozen at a time crawling around on top of the snow. Note: Jean Harrison, a fellow nature lover, just identified this larva as Noctua pronuba, a winter cutworm also known as the greater yellow underwing (moth), a recent immigrant from Europe.
If you pull apart a red, fuzzy seed head of Staghorn Sumac (Rhus typhina) this time of year, you will find, in addition to a multitude of seeds, a profusion of scat in the shape of miniscule round, grey balls. If you’re lucky, you’ll find the larval insect that produced this scat. Chances are, according to Charley Eisman, author of Tracks and Sign of Insects, that many of the resident insects are in the Gelechioidea family of moths. The larvae of these moths are consumers of Staghorn Sumac seeds, and judging from the amount of scat usually present, they spend a considerable amount of time inhabiting the seed heads. It’s likely that Black-capped Chickadees and other birds you see gleaning sumac fruit are actually there for the larvae as much as the seeds.